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Jaina Biology
epithelium into the capillaries, and carbon dioxide diffuses in the reverse direction".44
168
"Insects have quite a different system for getting oxygen to the cells. In each section or segment of the body is a pair of holes, called spiracles, from which a tracheal tube extends into the body, branching and rebranching until it reaches each cell".45
"The body walls of insects pulsate, drawing air into the trachea when the body expands, forcing air out when the body contracts. Thus, in contrast to a fish or crab, in which blood is brought to the surface of the body to be aerated in a gill, the tracheal system conducts air deep within the insect body, near enough to each cell so that it can diffuse in through the wall of the tracheal tube".46
44. Ibid.
45. Biology, p. 294.
46. Blology, p. 295
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